The size and weight of a system designed to defeat military equipment, improvised explosive devices (IEDs) or an incoming projectile are constrained by the need for both fragments to destroy the target and a structure to hold them. Loose fragments do not provide the mechanical support required for a stable device. A solid metal structure, such as a missile casing, is too sturdy to breakup easily or reliably. Patterning a solid structure facilitates breakup but reduces mechanical strength. In contrast, a solid material which provides mechanical strength yet fragments controllably offers a significant weight savings over existing systems.
Bonding fragments together into a larger structure that provides the necessary mechanical integrity, yet will breakup controllably on detonation, can achieve this weight saving. This enables the selection of fragments of a known mass, geometry and desired dispersion pattern, yet with the same strength as a solid structure. The challenge is in selecting a sufficiently strong bonding method that will breakup as desired. A variety of bonding methods exist, each with different strengths and weaknesses. Polymeric glue is simple, but lacks sufficient stiffness, strength or density comparable to metals. Fragments could also be isostatically pressed, either hot or cold, to remove voids, but large fragments will not bond strongly with such minimal material deformation.
Fragment effectiveness can be increased by replacing inert material with one that will release chemical energy on impact. The benefits of reactive fragments have previously been demonstrated. One effective fragment technology is known as reactive laminates, specifically intermetallic formation reactions such as the Al/Ni alloying reaction. This material adds chemical energy to the projectile's kinetic energy, generating a high temperature to drive eta fuel combustion. The Al/Ni reactive laminate is also a metal-metal composite, capable of providing the mechanical support needed in a reactive structure.
It would therefore be advantageous to provide a method for the fabrication of mm-scale reactive fragments and the subsequent consolidation of these particles into a larger, mechanically robust structure.